Emissions issue

[20b]

Hi all, new here - Proud owner of a 1997 UK-Spec MX-3 1.6 DOHC 107hp.

Not sure whether its better to get straight to the point or introduce myself and if this is the best place in the forum to introduce myself... Anyhow, bought the car in May and absolutely fell in love with it, it feels nothing like the cars I've owned before.

The car has about 107k miles, no mods apart from a upgraded exhaust which I bought earlier a few months back but now just want to change to the stock V6 exhaust... and a RX-8 front seat transplant which I did a few weeks ago.





Now to get to the point, I recently had to put the car through yearly inspection and it failed on Emissions - "HC"... I recently changed oil, changed oil filter, air filter, spark plugs and even MAF (My MAF died so car is now using a second hand MX-5 MAF since Mazda wanted 811 euro for a new one!)

I talked to a mechanic I trust about it and he believes it may need new piston rings which in total is about 200 for parts and 300 for work according to him... Though I am wondering if the catalytic converter might be playing a part in this? It rattles quite often and it is rusty with small holes in it/the casing around it.

Any opinions what it might be? also the car has been leaking some oil near the front of the engine but I check the oil levels regularly and they are fine - Infact it seems like the car barely uses any oil at all? my old audi/bmw and honda used much more oil than the MX3..

Don't know if this points at the piston rings but around 2-2.5k rpm the car sometimes has a "no power" zone - mostly in first/second gear, i.e you accelerate up to 2k, then it "freezes" for a second and jumps up about 500rpm.. and drives fine in the rpm range after that.

Sorry if this is a long post, but I wanted to make sure I didn't forget to mention anything which might help find the cause.

Thank you!

[kulluminati777]

I new catalytic converter should solve your issue. Check that your EGR is functioning correctly as well. I just passed strict california emissions and all I did was install a new catalytic converter. I had a K8DE in my car with the EGR functioning properly and an old CAT and I failed emissions. After my KLZE swap (no EGR at all) and a new CAT I passed no problems. Im sure HC is what the cat reduces anyway.....


We love long posts or any posts for that matter here. Also welcome to the forums. There is a UK site as well if you didnt know.


And are you sure your leak is the engine oil and not the power steering fluid.....maybe the front cooler is rusted out and leaking a tad bit

[Daninski]

First, 'Seafoam' your engine by removing a vac hose like your brake booster hose, plug with your figure or your engine will stall then ease figure off as you pour the Seafoam (1/3 can) into the hose while the engines running then shut engine off and let sit for 10-15 mins. Start car and watch the smoke fly.(Just Google Seafoam).
Second, using a ethanol blended fuel add about 10 oz of acetone to your gas tank, this will help you pass as well. (Google acetone additive to fuel for explanation).
Third, plugs new, disty cap and rotor new or contacts cleaned.
Finally read this page for an explanation of failure causes.
http://www.ene.gov.on.ca/stdprodconsume ... 087907.pdf

Any vaccum leak will definitely cause high Hc. double check all vac hoses the intake hose after the VAF in particular. Post [WTB] in want to buy section Vaf for your engine here. I'm sure members have those babies just sitting around.

Good Luck

[20b]

I'll probably get a new catalytic converter before changing my rings, if cat wont help then ill try the seafoam trick.
I'd try acetone too but pure acetone is quite hard to find here in Ireland.

Ill check if its power steering fluid that's leaking, would be surprised if it was though.

Thanks for the ideas!

[Savin]

I just use denatured alcohol. 1 gallon of it in a 1/4 tank of fuel. It'll almost read zero on all stats across the board.

To give you an idea, my 1989 mustang blew 5.4gpm for HC the test right before this. All I did was put in denatured alcohol. The only factory emissions equipment it had were the stock catalytic converters. EGR and smog pump had been removed. It also had a none emissions compliant cam.
.78 HC(limit 1.4) - 0.00 Co(limit 20.0) - .58 NOx(limit 3.0)

[20b]

I just use denatured alcohol. 1 gallon of it in a 1/4 tank of fuel. It'll almost read zero on all stats across the board.

Hmm, might try this too... thanks man

[SuperK]

If a "high flow" catalytic converter was used at any time, it's junk and needs to be replaced. Do you know what the HC numbers were looking like?

also, vacuum leaks after the air flow meter and TPS could cause it to show high HCs. Try retarding the timing a bit as well.

[kulluminati777]

I forgot I used denatured alchohol as well. poured a gallon into my tank that was 1/4th full. If its strict like cali they check the timing and make sure its spot on to oem specs. I didnt know that about the vac leaks and high HC though. I learn something every time im on here

[20b]

If a "high flow" catalytic converter was used at any time, it's junk and needs to be replaced. Do you know what the HC numbers were looking like?

also, vacuum leaks after the air flow meter and TPS could cause it to show high HCs. Try retarding the timing a bit as well.

No idea if a high-flow cat was used before, I think a stock one is there at the moment but it's rusting and there's small holes in the shield (maybe even in cat itself, not sure).

Here is the emissions part of the inspection sheet:



Also, the air flow meter was replaced recently (by a second-hand MX-5 one) and the vacuum hose that goes between it and the engine was replaced recently - brand new directly from Mazda.

[mazdaspeed23]

could be the cat, I use methyl hydrate when going into etest. I pour the whole bottle in let it run for about 15 minutes, then take the car for hard drive ( opening it wide) cleaning it all out get it really hot, then take it in. the hotter the car is the more cleaner it burns. So I've read and heard from several of people. Works every time for me. but I'm sure that denatured alcohol works great aswell, agreed with Dan that Seafoam works wonders. could also be a 02 sensor

[Josh]

The stock cat on these is kind of crap, there are actually two. One just under the header and another further down in the straight section. The second one is the one that tends to rust out and go bad as they are an odd design.

It is very very unlikely that your rings are bad especially at 107K kilometers. You would know if they were bad on this engine as it would smoke. and the price you have been quoted is very cheap for just a ring job. usually it would be closer to 1K and it usually means a full lower rebuild of the engine at that point. Though if it is smoking (and it would be blue smoke) the number one cause in these engines is the valve seals. these are a tedious but inexpensive part that does fail after 100-150K miles at least here in the US.

With your oil leak, the front main seals tend to dry up and seap on these engines as well and probably the cause of your oil drip. Also an inexpensive replacement. If you change that one it may be beneficial for you to also change out the Cam seal, the valve cover seal, as well as the distributor seal, as these are all also points where they tend to leak and are fairly inexpensive and straightforward to replace.

Your RPM jump is a bit odd and the cat would not cause it to function that way. These years of 1.6L use an internal coil and they also have a tendency to fail over time, it may be beneficial for you to look into an HEI mod and or an external coil swap. When they start to go out it causes the tach to do funny things like jump RPMs.

Your car looks great BTW. I think you should do as was suggested and Seafoam it, replace the cat and add some acetone or denatured alcohol to your fuel and you should probably be good to go.

[Daninski]

You never said if the car had been sitting for long before you bought it. If so 2 tanks of gas need to go through it first then Etest it. Being OBD2 if there was a serious issue you should be throwing a code. You have O2 sensor monitors that are located after the actual O2 sensors so. If the O2 sensors were bad you would get a code for them. Make sure your running high test gas and add a fuel injector cleaner in as well. By the way, adding acetone to your fuel only works with ethanol blended fuels and adding alcohol can burn your valves so get rid of that sh*t after your Etest. Cheers.

[20b]

Thanks for the help, and when I bought the car it was sitting for about 2 months, I've driven it for a good few months before I went through the inspection though. The car is not OBD1 or OBD2 it seems, as even Mazda centre had to scan it as an MX-5 with some older equipment.

Sorry for the late reply, and thanks for the suggestions everyone!

On a side note, I've lowered ignition timing to try and see if that helps pass through emissions, she has HORRIBLE smoke on cold starts like so: http://www.youtube.com/watch?v=QoeOSiBL7uE but once the car warms up after 5 minutes idling (I always let her warm up for 5 minutes even if she's been off for an hour) the smoke goes away. I have talked with another mechanic and he says I need valve cover seals and a few other things replaced which I can't remember of for now. Is there anyway to convert the car to OBD2? I'd love to use one of those real-time engine info apps like torque.

Edit: Forgot to add, she had 3 compression tests within last 4 months, most recent one being 2 weeks ago and all the tests confirmed that the compression is perfect.. I'll have my inspection again tomorrow along with emissions so will hopefully pass with my lowered ignition timing.

[Josh]

Chances are that if it is smoking like that when cold then it is the valve guide seals. They are very well known for going out on this motor.

The thing with OBDII Mx-3's.. They were all OBDI in reality, in the US and Canada they changed them to OBDII in 96', but it is not a "true" OBDII. It is an OBDI system fooling to an OBDII. Most other countries had a "cross over" variant in 97'-98' and it is really neither. I myself would love to get my hands on an MX-6 harness from these years so I could run the KLK1 ECU which is the last factory tuned ECU by Mazda for the KLZE. From what I remember is that only the US had the OBDII diag ports, but I could be wrong. I think OBDII was a mandatory crossover in 02' in most of the world. Or 98' I don't remember for sure.

[20b]

I see, thanks and yea the valve seals was something along the lines my mechanic said.

Good news is I passed emissions but barely (got 0.30 and limit was 0.30). The Ignition timing trick seemed to work.

Ill have the valve guide seals replaced soon, need to get my timing belt done first.

Thanks everyone.